La palabra del día: Solicitud

Feminine noun. From the Latin sollicitūdo. In Legal and Business Spanish is a letter or document in which something is officially requested, an application form. The verb is solicitar. If you are applying for a job, the expression is rellenar una/la solicitud de trabajo. The same if you are requesting anything from an authority, e.g.: solicitud de exención contributiva, solicitar una exención impositiva.
If you are applying to the university, we use inscribirse en la universidad. If you are filling the application form to join a gym or a club, it is used inscribirse en un gimnasio/un club. Please do not use aplicar para el gimnasio, etc., even if you hear it from your Spanish speaking friends. It is not just wrong, it also sounds awful. dc